GMTDate

: day of month from 1 to 31

an instance of the corresponding day of week

: day of year from 1 to 366

: hours from 0 to 23

: minutes from 0 to 59

an instance of the corresponding month

: seconds from 0 to 60(last is for leap second)

is a number of epoch milliseconds

: year in common era(CE: https://en.wikipedia.org/wiki/Common_Era)

Subtracts the specified number of milliseconds

Subtracts the specified duration

Adds the specified number of milliseconds

Adds the specified duration

Convert to Date

Truncate to seconds by discarding sub-second part